My brother told me of when the STOP light came on on his semi tractor.. And he did, but not before the engine developed a split personality.. he called his boss, then he called Detroit Diesel and a buddy dropped his trailer at the nearby truck stop and they doubled back to pick up little brother's (Well not so little, 6'6 1/2" tall) and the tow truck from double D was already there getting ready to take the tractor to a repair shop.> Double D air-freighted both a new engine and a technician/engineer and he was on the road within 24 hours again, For a Professional Semi driver TIME really IS money.
On my car I get Check engine (And thank you for the reminder) lights all the time.. I keep a reader on the debris tray (you know, the tray where stuff seems to collect) usually it's 455 (Evaporative Emissions control major fault,, No there is no fault, just a sticky valve) but hey.. Nice to knwo the code.